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Overview
Comment:Fix for ticket #42: Added comments to structs Trigger, TriggerStep and TriggerStack. (CVS 569)
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SHA1:9ec8a2b139ce38312284d7b4eb61221b1e1e3052
User & Date: danielk1977 2002-05-16 00:13:12
Context
2002-05-17
00:05
Stylistic changes to src/trigger.c (partial fix to ticket #39). Also more comments. (CVS 570) check-in: b1d72cb5 user: danielk1977 tags: trunk
2002-05-16
00:13
Fix for ticket #42: Added comments to structs Trigger, TriggerStep and TriggerStack. (CVS 569) check-in: 9ec8a2b1 user: danielk1977 tags: trunk
2002-05-15
23:26
Fix a typo in the c_interface.html documentation file. (CVS 568) check-in: 454879fa user: drh tags: trunk
Changes
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Changes to src/sqliteInt.h.

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**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.109 2002/05/15 12:45:43 drh Exp $
*/
#include "sqlite.h"
#include "hash.h"
#include "vdbe.h"
#include "parse.h"
#include "btree.h"
#include <stdio.h>
................................................................................
  int useAgg;          /* If true, extract field values from the aggregator
                       ** while generating expressions.  Normally false */
  int schemaVerified;  /* True if an OP_VerifySchema has been coded someplace
                       ** other than after an OP_Transaction */
  TriggerStack *trigStack;
};



struct TriggerStack {
  Trigger *pTrigger;
  Table *pTab;         /* Table that triggers are currently being coded as */
  int newIdx;          /* Index of "new" temp table */

  int oldIdx;          /* Index of "old" temp table */
  int orconf;          /* Current orconf policy */

























  TriggerStack *pNext;













};





































struct TriggerStep {
  int op;               /* One of TK_DELETE, TK_UPDATE, TK_INSERT, TK_SELECT */
  int orconf;

  Select *pSelect;     /* Valid for SELECT and sometimes 
			   INSERT steps (when pExprList == 0) */
  Token target;         /* Valid for DELETE, UPDATE, INSERT steps */
  Expr *pWhere;        /* Valid for DELETE, UPDATE steps */
  ExprList *pExprList; /* Valid for UPDATE statements and sometimes 
			   INSERT steps (when pSelect == 0)         */
  IdList *pIdList;      /* Valid for INSERT statements only */

  TriggerStep * pNext;  /* Next in the link-list */
};




























struct Trigger {
  char *name;             /* The name of the trigger                        */
  char *table;            /* The table or view to which the trigger applies */
  int op;                 /* One of TK_DELETE, TK_UPDATE, TK_INSERT         */
  int tr_tm;              /* One of TK_BEFORE, TK_AFTER, TK_INSTEAD         */
  Expr *pWhen;            /* The WHEN clause of the expresion (may be NULL) */
  IdList *pColumns;       /* If this is an UPDATE OF <column-list> trigger,
                             the column names are stored in this list       */
  int foreach;            /* One of TK_ROW or TK_STATEMENT */






  TriggerStep *step_list; /* Link list of trigger program steps             */
  char *strings;          /* pointer to allocation of Token strings */
  Trigger *pNext;         /* Next trigger associated with the table */
  int isCommit;

};






extern int always_code_trigger_setup;


/*
** Internal function prototypes
*/
int sqliteStrICmp(const char *, const char *);
int sqliteStrNICmp(const char *, const char *, int);
int sqliteHashNoCase(const char *, int);







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**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.110 2002/05/16 00:13:12 danielk1977 Exp $
*/
#include "sqlite.h"
#include "hash.h"
#include "vdbe.h"
#include "parse.h"
#include "btree.h"
#include <stdio.h>
................................................................................
  int useAgg;          /* If true, extract field values from the aggregator
                       ** while generating expressions.  Normally false */
  int schemaVerified;  /* True if an OP_VerifySchema has been coded someplace
                       ** other than after an OP_Transaction */
  TriggerStack *trigStack;
};

/*
 * Each trigger present in the database schema is stored as an instance of
 * struct Trigger. 



 *
 * Pointers to instances of struct Trigger are stored in two ways.
 * 1. In the "trigHash" hash table (part of the sqlite* that represents the 
 *    database). This allows Trigger structures to be retrieved by name.
 * 2. All triggers associated with a single table form a linked list, using the
 *    pNext member of struct Trigger. A pointer to the first element of the linked
 *    list is stored as the "pTrigger" member of the associated struct Table.
 *
 * The "strings" member of struct Trigger contains a pointer to the memory 
 * referenced by the various Token structures referenced indirectly by the
 * "pWhen", "pColumns" and "step_list" members. (ie. the memory allocated for
 * use in conjunction with the sqliteExprMoveStrings() etc. interface).
 *
 * The "step_list" member points to the first element of a linked list containing
 * the SQL statements specified as the trigger program.
 *
 * When a trigger is initially created, the "isCommit" member is set to FALSE.
 * When a transaction is rolled back, any Trigger structures with "isCommit" set
 * to FALSE are deleted by the logic in sqliteRollbackInternalChanges(). When
 * a transaction is commited, the "isCommit" member is set to TRUE for any
 * Trigger structures for which it is FALSE.
 *
 * When a trigger is dropped, using the sqliteDropTrigger() interfaced, it is 
 * removed from the trigHash hash table and added to the trigDrop hash table. If 
 * the transaction is rolled back, the trigger is re-added into the trigHash
 * hash table (and hence the database schema). If the transaction is commited,
 * then the Trigger structure is deleted permanently.
 */
struct Trigger {
  char *name;             /* The name of the trigger                        */
  char *table;            /* The table or view to which the trigger applies */
  int op;                 /* One of TK_DELETE, TK_UPDATE, TK_INSERT         */
  int tr_tm;              /* One of TK_BEFORE, TK_AFTER */
  Expr *pWhen;            /* The WHEN clause of the expresion (may be NULL) */
  IdList *pColumns;       /* If this is an UPDATE OF <column-list> trigger,
                             the <column-list> is stored here */
  int foreach;            /* One of TK_ROW or TK_STATEMENT */

  TriggerStep *step_list; /* Link list of trigger program steps             */
  char *strings;          /* pointer to allocation of Token strings */
  Trigger *pNext;         /* Next trigger associated with the table */
  int isCommit;           /* Set to TRUE once the trigger has been committed */
};

/*
 * An instance of struct TriggerStep is used to store a single SQL statement
 * that is a part of a trigger-program. 
 *
 * Instances of struct TriggerStep are stored in a singly linked list (linked
 * using the "pNext" member) referenced by the "step_list" member of the 
 * associated struct Trigger instance. The first element of the linked list is
 * the first step of the trigger-program.
 * 
 * The "op" member indicates whether this is a "DELETE", "INSERT", "UPDATE" or
 * "SELECT" statement. The meanings of the other members is determined by the 
 * value of "op" as follows:
 *
 * (op == TK_INSERT)
 * orconf    -> stores the ON CONFLICT algorithm
 * pSelect   -> If this is an INSERT INTO ... SELECT ... statement, then
 *              this stores a pointer to the SELECT statement. Otherwise NULL.
 * target    -> A token holding the name of the table to insert into.
 * pExprList -> If this is an INSERT INTO ... VALUES ... statement, then
 *              this stores values to be inserted. Otherwise NULL.
 * pIdList   -> If this is an INSERT INTO ... (<column-names>) VALUES ... 
 *              statement, then this stores the column-names to be inserted into.
 *
 * (op == TK_DELETE)
 * target    -> A token holding the name of the table to delete from.
 * pWhere    -> The WHERE clause of the DELETE statement if one is specified.
 *              Otherwise NULL.
 * 
 * (op == TK_UPDATE)
 * target    -> A token holding the name of the table to update rows of.
 * pWhere    -> The WHERE clause of the UPDATE statement if one is specified.
 *              Otherwise NULL.
 * pExprList -> A list of the columns to update and the expressions to update
 *              them to. See sqliteUpdate() documentation of "pChanges" argument.
 * 
 */
struct TriggerStep {
  int op;              /* One of TK_DELETE, TK_UPDATE, TK_INSERT, TK_SELECT */
  int orconf;          /* OE_Rollback etc. */

  Select *pSelect;     /* Valid for SELECT and sometimes 
			  INSERT steps (when pExprList == 0) */
  Token target;        /* Valid for DELETE, UPDATE, INSERT steps */
  Expr *pWhere;        /* Valid for DELETE, UPDATE steps */
  ExprList *pExprList; /* Valid for UPDATE statements and sometimes 
			   INSERT steps (when pSelect == 0)         */
  IdList *pIdList;     /* Valid for INSERT statements only */

  TriggerStep * pNext; /* Next in the link-list */
};

/*
 * An instance of struct TriggerStack stores information required during code
 * generation of a single trigger program. While the trigger program is being
 * coded, its associated TriggerStack instance is pointed to by the
 * "pTriggerStack" member of the Parse structure.
 *
 * The pTab member points to the table that triggers are being coded on. The 
 * newIdx member contains the index of the vdbe cursor that points at the temp
 * table that stores the new.* references. If new.* references are not valid
 * for the trigger being coded (for example an ON DELETE trigger), then newIdx
 * is set to -1. The oldIdx member is analogous to newIdx, for old.* references.
 *
 * The ON CONFLICT policy to be used for the trigger program steps is stored 
 * as the orconf member. If this is OE_Default, then the ON CONFLICT clause 
 * specified for individual triggers steps is used.
 *
 * struct TriggerStack has a "pNext" member, to allow linked lists to be
 * constructed. When coding nested triggers (triggers fired by other triggers)
 * each nested trigger stores its parent trigger's TriggerStack as the "pNext" 
 * pointer. Once the nested trigger has been coded, the pNext value is restored
 * to the pTriggerStack member of the Parse stucture and coding of the parent
 * trigger continues.
 *
 * Before a nested trigger is coded, the linked list pointed to by the 
 * pTriggerStack is scanned to ensure that the trigger is not about to be coded
 * recursively. If this condition is detected, the nested trigger is not coded.
 */
struct TriggerStack {








  Table *pTab;         /* Table that triggers are currently being coded on */
  int newIdx;          /* Index of vdbe cursor to "new" temp table */
  int oldIdx;          /* Index of vdbe cursor to "old" temp table */
  int orconf;          /* Current orconf policy */
  Trigger *pTrigger;





  TriggerStack *pNext;
};

/*
 * This global flag is set for performance testing of triggers. When it is set
 * SQLite will perform the overhead of building new and old trigger references 
 * even when no triggers exist
 */
extern int always_code_trigger_setup;


/*
** Internal function prototypes
*/
int sqliteStrICmp(const char *, const char *);
int sqliteStrNICmp(const char *, const char *, int);
int sqliteHashNoCase(const char *, int);